Roche ($RHHBY) has picked up another encouraging snapshot of promising early data for its PD-L1 checkpoint star atezolizumab--this time from a combination study involving triple negative breast cancer.

Investigators paired atezo (MPDL3280A) with nab-paclitaxel among 32 metastatic patients. They tracked an overall tumor response rate of 71% with 11 of 17 (65%) responses continuing at data cutoff. And the researchers noted that the responses occurred among patients who were both PD-L1 positive and PD-L1 negative, highlighting a synergistic impact in a broad segment of the patients in the small, proof-of-concept study.

Merck ($MRK) and Bristol-Myers Squibb ($BMY) have gone all out to expand the approval of their PD-1 drugs, one part of a biologic hurdle that cancer cells use to thwart an immune system attack. Roche and AstraZeneca ($AZN) have been hard at it on the other side of that equation, looking for data that are just as good if not better than the first market entries, Keytruda and Opdivo. The Pfizer ($PFE)/Merck KGaA team is in fifth-place position with their own checkpoint inhibitor.

NYU's Sylvia Adams

Citing the high response rate, Dr. Sylvia Adams, an associate professor of medicine at the NYU Perlmutter Cancer Center, told OncLive: "The combination was well-tolerated without additive toxicity. We saw only toxicity that was predictable for the single agents alone."

"Patients with TNBC usually have low response rates to conventional chemotherapy and quick progression in the metastatic disease setting," added Adams. "Therefore, the response rate, and particularly the durability of responses, seen were remarkable. Several patients have now been treated for over one year."

Roche has already moved into Phase III on triple negative breast cancer, looking to parlay a slate of data points on a wide variety of cancer targets as it plays catchup in the multibillion-dollar checkpoint inhibitor R&D race. Back in July, Roche said it would take its promising Phase II bladder cancer data on atezolizumab to the FDA, to determine the possibility of an accelerated approval. And in the meantime it set up 11 Phase III studies in a program involving 36 studies.

"We are encouraged that a high proportion of people responded to combined treatment with atezolizumab and nab-paclitaxel chemotherapy, regardless of their PD-L1 expression," said Dr. Sandra Horning, Roche's chief medical officer and head of global product development. "This result indicates that combinations may provide a way to increase the benefits of atezolizumab in a wide range of people with triple-negative breast cancer."